U.S. patent application number 17/289753 was filed with the patent office on 2021-12-02 for multilayer magnetic tunnel junction etching method and mram device.
This patent application is currently assigned to JIANGSU LEUVEN INSTRUMENTS CO. LTD. The applicant listed for this patent is JIANGSU LEUVEN INSTRUMENTS CO. LTD. Invention is credited to Dongchen CHE, Lu CHEN, Hushan CUI, Dajian HAN, Dongdong HU, Zhongyuan JIANG, Ziming LIU, Juebin WANG, Kaidong XU, Zhiwen ZOU.
Application Number | 20210376232 17/289753 |
Document ID | / |
Family ID | 1000005793832 |
Filed Date | 2021-12-02 |
United States Patent
Application |
20210376232 |
Kind Code |
A1 |
WANG; Juebin ; et
al. |
December 2, 2021 |
MULTILAYER MAGNETIC TUNNEL JUNCTION ETCHING METHOD AND MRAM
DEVICE
Abstract
A multilayer magnetic tunnel junction etching method and an MRAM
device. A wafer is processed according to particular steps without
interrupting vacuum. A reactive ion plasma etching chamber (10) and
an ion beam etching chamber (11) are used separately at least one
time. The processing of a multilayer magnetic tunnel junction is
always in a vacuum environment, thereby avoiding the impact of an
external environment on etching. By means of the process of
combining etching and cleaning, a device structure maintains good
steepness, and the metal contamination and damage of a magnetic
tunnel junction film structure are significantly decreased, thereby
greatly increasing the performance and reliability of a device. In
addition, use of both the ion beam etching chamber (11) and the
reactive ion plasma etching chamber (10) solves the technical
problem of an existing single etching method, and increases
production efficiency and etching process precision.
Inventors: |
WANG; Juebin; (Jiangsu,
CN) ; JIANG; Zhongyuan; (Jiangsu, CN) ; LIU;
Ziming; (Jiangsu, CN) ; CHE; Dongchen;
(Jiangsu, CN) ; CUI; Hushan; (Jiangsu, CN)
; HU; Dongdong; (Jiangsu, CN) ; CHEN; Lu;
(Jiangsu, CN) ; HAN; Dajian; (Jiangsu, CN)
; ZOU; Zhiwen; (Jiangsu, CN) ; XU; Kaidong;
(Jiangsu, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JIANGSU LEUVEN INSTRUMENTS CO. LTD |
Jiangsu |
|
CN |
|
|
Assignee: |
JIANGSU LEUVEN INSTRUMENTS CO.
LTD
Jiangsu
CN
|
Family ID: |
1000005793832 |
Appl. No.: |
17/289753 |
Filed: |
May 23, 2019 |
PCT Filed: |
May 23, 2019 |
PCT NO: |
PCT/CN2019/088104 |
371 Date: |
April 29, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 43/02 20130101;
H01L 43/10 20130101; H01L 27/222 20130101; H01L 43/08 20130101;
G11C 11/161 20130101; H01L 21/3065 20130101; H01L 43/12
20130101 |
International
Class: |
H01L 43/12 20060101
H01L043/12; H01L 43/02 20060101 H01L043/02; H01L 43/08 20060101
H01L043/08; H01L 43/10 20060101 H01L043/10; H01L 27/22 20060101
H01L027/22; H01L 21/3065 20060101 H01L021/3065; G11C 11/16 20060101
G11C011/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2018 |
CN |
201811325940.2 |
Claims
1. A multilayer magnetic tunnel junction (MTJ) etching method,
using an etching device comprising a sample loading chamber, a
vacuum transition chamber, a reactive ion plasma etching chamber,
an ion beam etching (IBE) chamber, a film coating chamber, and a
vacuum transport chamber, wherein the vacuum transition chamber is
connected to the sample loading chamber and the vacuum transport
chamber separately in a linkable manner; the reactive ion plasma
etching chamber, the IBE chamber, and the film coating chamber are
separately connected to the vacuum transport chamber in a linkable
manner; a sample is processed without interrupting the vacuum, and
the reactive ion plasma etching chamber and the IBE chamber are
separately used at least one time; and the method comprises the
following steps: a sample preparation step and a sample loading
step: loading the sample to the sample loading chamber, and the
sample entering the vacuum transport chamber through the vacuum
transition chamber, wherein the sample is formed on a semiconductor
substrate and comprises a bottom electrode, an MTJ, a cap layer,
and a mask layer; the MTJ comprises a pinned layer, an isolation
layer, and a free layer; and there are multiple isolation layers
and free layers; a first etching step: the sample entering the
reactive ion plasma etching chamber or the IBE chamber, completing
etching for the cap layer and the free layer and stopping etching
at a first isolation layer, and then the sample returning to the
vacuum transport chamber; a first cleaning step: the sample
entering the IBE chamber or the reactive ion plasma etching
chamber, and removing metallic residues and treating a sample
surface, so that metal contamination and a sidewall damage layer
formed in the first etching step are completely removed; and then
the sample returning to the vacuum transport chamber; a first
dielectric coating step: the sample entering the film coating
chamber, and forming a first dielectric thin film on the upper
surface of and around the sample; and then the sample returning to
the vacuum transport chamber; a first dielectric thin film opening
step: the sample entering the reactive ion plasma etching chamber
or the IBE chamber, opening the first dielectric thin film on the
top and bottom portions of the device but leaving the part on a
device sidewall, and stopping etching; and then the sample
returning to the vacuum transport chamber; repeating the foregoing
steps, wherein each etching is stopped at the next isolation layer
till a bottommost isolation layer; a final etching step: the sample
entering the reactive ion plasma etching chamber or the IBE
chamber, etching the sample, and stopping etching at a bottom
electrode metal layer; and then the sample returning to the vacuum
transport chamber; a final cleaning step: the sample entering the
IBE chamber or the reactive ion plasma etching chamber, and
removing metallic residues and treating a sample surface, so that
the metal contamination and sidewall damage layer formed in the
final etching step are completely removed; and then the sample
returning to the vacuum transport chamber; a final dielectric
coating step: the sample entering the film coating chamber for
coating protection, and forming a final dielectric thin film on the
upper surface of and around the sample; and then, the sample
returning to the vacuum transport chamber; and a sample take-out
step: the sample returning from the vacuum transport chamber to the
sample loading chamber through the vacuum transition chamber.
2. The multilayer MTJ etching method according to claim 1, wherein
gas used in the etching or cleaning step in the reactive ion plasma
etching chamber is inert gas, nitrogen, oxygen, fluorine-based gas,
NH.sub.3, amino gas, CO, CO.sub.2, alcohol, or a combination
thereof; and the gas, power, airflows, and pressure that are used
in different steps are identical or different.
3. The multilayer MTJ etching method according to claim 1, wherein
gas used in the etching or cleaning step in the IBE chamber is
inert gas, nitrogen, oxygen, or a combination thereof; and the gas,
ion beam angles, ion beam energy, and ion beam density that are
used in different steps are identical or different.
4. The multilayer MTJ etching method according to claim 1, wherein
materials of the first dielectric thin film and the final
dielectric thin film are identical or different; the material of
the first dielectric thin film or the final dielectric thin film is
a group IV oxide, group IV nitride, group IV nitrogen oxide,
transition metal oxide, transition metal nitride, transition metal
nitrogen oxide, alkaline earth metal oxide, alkaline earth metal
nitride, alkaline earth metal nitrogen oxide, or a combination
thereof; and the materials of the first dielectric thin film are
identical or different in different first dielectric coating
steps.
5. A magnetic random access memory (MRAM) device, comprising a
multilayer magnetic tunnel junction (MTJ) prepared by using the
multilayer MTJ etching method according to claim 1, wherein each
isolation layer and a free layer above the isolation layer in the
multilayer MTJ present a step-like structure.
6. A multilayer magnetic tunnel junction (MTJ) etching method,
using an etching device comprising a sample loading chamber, a
vacuum transition chamber, a reactive ion plasma etching chamber,
an ion beam etching (IBE) chamber, a film coating chamber, and a
vacuum transport chamber, wherein the vacuum transition chamber is
connected to the sample loading chamber and the vacuum transport
chamber separately in a linkable manner; the reactive ion plasma
etching chamber, the IBE chamber, and the film coating chamber are
separately connected to the vacuum transport chamber in a linkable
manner; characterized in that, a sample is processed without
interrupting the vacuum, and the reactive ion plasma etching
chamber and the IBE chamber are separately used at least one time;
and the method comprises the following steps: a sample loading
step: loading the sample to the sample loading chamber, and the
sample entering the vacuum transport chamber through the vacuum
transition chamber, wherein the sample is formed on a semiconductor
substrate and comprises a bottom electrode, an MTJ, a cap layer,
and a mask layer; the MTJ comprises a pinned layer, an isolation
layer, and a free layer; and there are multiple isolation layers
and free layers; a first etching step: the sample entering the IBE
chamber or the reactive ion plasma etching chamber, etching the
sample, and stopping etching at a particular isolation layer; and
then the sample returning to the vacuum transport chamber; a first
cleaning step: the sample entering the reactive ion plasma etching
chamber or the IBE chamber, and removing metallic residues and
treating a sample surface, so that metal contamination and a
sidewall damage layer formed in the first etching step are
completely removed; and then the sample returning to the vacuum
transport chamber; a first dielectric coating step: the sample
entering the film coating chamber, and forming a first dielectric
thin film on the upper surface of and around the sample; and then
the sample returning to the vacuum transport chamber; a first
dielectric thin film opening step: the sample entering the reactive
ion plasma etching chamber or the IBE chamber, opening the first
dielectric thin film on the top and bottom portions of the device
but leaving the part on a device sidewall, and stopping etching;
and then the sample returning to the vacuum transport chamber; a
second etching step: the sample entering the reactive ion plasma
etching chamber or the IBE chamber, etching the remaining layers of
the sample, and stopping etching at a bottom electrode metal layer;
and then the sample returning to the vacuum transport chamber; a
second cleaning step: the sample entering the IBE chamber or the
reactive ion plasma etching chamber, and removing metallic residues
and treating a sample surface, so that the metal contamination and
sidewall damage layer formed in the second etching step are
completely removed; and then the sample returning to the vacuum
transport chamber; a second dielectric coating step: the sample
entering the film coating chamber for coating protection, and
forming a second dielectric thin film on the upper surface of and
around the sample; and then, the sample returning to the vacuum
transport chamber; and a sample take-out step: the sample returning
from the vacuum transport chamber to the sample loading chamber
through the vacuum transition chamber.
7. The multilayer MTJ etching method according to claim 6, wherein
an etching or cleaning angle in the IBE chamber ranges from
10.degree. to 80.degree., which is an included angle between an ion
beam and a normal face of a sample stage.
8. The multilayer MTJ etching method according to claim 6, wherein
the first dielectric thin film has a thickness of 0.5 nm to 5 nm,
and the second dielectric thin film has a thickness of 1 nm to 500
nm.
9. The multilayer MTJ etching method according to claim 6, wherein
the MTJ sidewall with a thickness of 0.1 nm to 10.0 nm is removed
separately in the first cleaning step and the second cleaning
step.
10. A magnetic random access memory (MRAM) device, comprising a
multilayer magnetic tunnel junction (MTJ) prepared by using the
multilayer MTJ etching method according to claim 6, wherein an
isolation layer at which etching is stopped in the first etching
step and a free layer above the isolation layer in the multilayer
MTJ present a step-like structure.
Description
BACKGROUND
Technical Field
[0001] The present invention relates to the field of semiconductor
technologies, and in particular, to a multilayer magnetic tunnel
junction (MTJ) etching method and a magnetic random access memory
(MRAM) device.
[0002] A magnetic memory is an important part of the computer
architecture and has a decisive impact on the speed, integration,
and power consumption of the computer. However, it is difficult for
the existing memory to achieve various performance indicators. For
example, a hard disk has a high storage capacity (which may reach
up to 1.3 Tb/in.sup.2) but a rather slow access speed (in
microseconds). On the contrary, a cache has a high speed but low
integration. In order to take full advantages of various memories,
a typical computer storage system uses a hierarchical structure. On
one hand, frequently used instructions and data are stored in the
cache and the main memory, so as to rapidly interact with a central
processing unit. On the other hand, a large number of infrequently
used system programs and files are stored in a high-density hard
disk (an HDD or SSD). By using such a hierarchical structure, the
storage system combines the advantages of a high speed and high
capacity. However, as the feature size of a semiconductor process
is further reduced, the conventional cache and main memory based on
a complementary metal oxide semiconductor (CMOS) process hit a
performance bottleneck. In terms of power consumption, since the
leakage current of a CMOS transistor increases with the reduction
of the process size, the static power consumption of the SRAM and
DRAM increasingly grows. As for the speed, the interconnect delay
between the processor and the memory limits the main frequency of
the system. An effective way to solve this problem is to construct
a non-volatile cache and main memory, so that the system can work
in a sleep mode but won't lose data, thus eliminating the leakage
current and static power consumption. Moreover, the non-volatile
memory can be directly integrated on a CMOS circuit by means of a
back-of-end-line technique, reducing the interconnect delay. The
STT-MRAM can achieve a good compromise in terms of speed, area,
write times, and power consumption, and thus is considered as an
ideal device for building a next-generation non-volatile cache and
main memory in the industry.
[0003] A core part of an MTJ is a sandwich structure formed by
sandwiching a tunneling barrier layer between two ferromagnetic
metal layers. One of the ferromagnetic layers is referred as a
reference layer or a pinned layer and its magnetization is fixed
along an easy-axis direction. The other ferromagnetic layer is
referred as a free layer, and its magnetization has two stable
directions which are parallel or antiparallel to the pinned layer.
Thus, the MTJ is rendered in a low resistance state or high
resistance state. This phenomenon is referred to as tunnel
magnetoresistance (TMR), and these two resistance states may be
represented respectively by using "0" and "1" in binary data.
[0004] An etching method is still required as the principal method
for MTJ patterning. It is relatively difficult for the material of
the MTJ to produce volatile products as compared with a dry etching
material such as Fe, Co, or Mg; and further an etchant gas (for
example, Cl.sub.2) cannot be used, or otherwise the performance of
the MTJ is degraded. Therefore, MTJ patterning can be realized by
necessarily using a relatively complicated etching method, and an
etching process is very difficult and challenging. The conventional
etching of large-size MTJs is generally realized by means of ion
beam etching (IBE). Because the IBE process uses inert gas,
basically no chemical etching component is introduced into a
reaction chamber, so that an MTJ sidewall is protected from
chemical erosion. Under the condition of ensuring a clean sidewall,
a perfect MTJ sidewall which is clean and not chemically damaged
can be obtained by means of IBE. However, IBE also has
shortcomings. On one hand, one implementation principle of the IBE
is the use of a high physical bombardment force, but an excessively
large physical bombardment force may cause disturbance in the
ordering of atomic layers of the MTJ sidewall, especially in the
isolation layer and the nearby core layer, thus disrupting the
magnetic characteristics of the MTJ. On the other hand, IBE is
realized necessarily by using a certain angle, which brings
limitations to the IBE. As MTJ devices are made increasingly
smaller in size, the MTJ films and the mask cannot be endlessly
compressed in thickness. The MTJ devices with a thickness of 30 nm
or less generally have a height-to-width ratio of above 2:1, and a
smaller size of the MTJ results in a higher height-to-width ratio.
At this height-to-width ratio, IBE cannot be performed to the
bottom of the MTJ at a frequently used angle, thus failing to meet
the requirement for separation of the MTJ devices, and making the
patterning fail. In addition, an IBE time is relatively long,
causing a limited yield of each apparatus.
SUMMARY
[0005] To solve the foregoing problem, the present invention
discloses a multilayer MTJ etching method, which uses an etching
device including a sample loading chamber, a vacuum transition
chamber, a reactive ion plasma etching chamber, an IBE chamber, a
film coating chamber, and a vacuum transport chamber, where the
vacuum transition chamber is connected to the sample loading
chamber and the vacuum transport chamber separately in a linkable
manner; the reactive ion plasma etching chamber, the IBE chamber,
and the film coating chamber are separately connected to the vacuum
transport chamber in a linkable manner; a sample is processed
without interrupting the vacuum, and the reactive ion plasma
etching chamber and the
[0006] IBE chamber are separately used at least one time. The
method includes following steps: a sample preparation step and a
sample loading step: loading the sample to the sample loading
chamber, and the sample entering the vacuum transport chamber
through the vacuum transition chamber, where the sample is formed
on a semiconductor substrate and includes a bottom electrode, an
MTJ, a cap layer, and a mask layer; the MTJ includes a pinned
layer, an isolation layer, and a free layer; and there are multiple
isolation layers and free layers; a first etching step: the sample
entering the reactive ion plasma etching chamber or the IBE
chamber, completing etching for the cap layer and the free layer
and stopping etching at a first isolation layer, and then the
sample returning to the vacuum transport chamber; a first cleaning
step: the sample entering the IBE chamber or the reactive ion
plasma etching chamber, and removing metallic residues and treating
a sample surface, so that metal contamination and a sidewall damage
layer formed in the first etching step are completely removed; and
then the sample returning to the vacuum transport chamber; a first
dielectric coating step: the sample entering the film coating
chamber, and forming a first dielectric thin film on the upper
surface of and around the sample; and then the sample returning to
the vacuum transport chamber; a first dielectric thin film opening
step: the sample entering the reactive ion plasma etching chamber
or the IBE chamber, opening the first dielectric thin film on the
top and bottom portions of the device but leaving the part on a
device sidewall, and stopping etching; and then the sample
returning to the vacuum transport chamber; repeating the foregoing
steps, where each etching is stopped at the next isolation layer
till a bottommost isolation layer; a final etching step: the sample
entering the reactive ion plasma etching chamber or the IBE
chamber, etching the sample, and stopping etching at a bottom
electrode metal layer; and then the sample returning to the vacuum
transport chamber; a final cleaning step: the sample entering the
IBE chamber or the reactive ion plasma etching chamber, and
removing metallic residues and treating a sample surface, so that
the metal contamination and sidewall damage layer formed in the
final etching step are completely removed; and then the sample
returning to the vacuum transport chamber; a final dielectric
coating step: the sample entering the film coating chamber for
coating protection, and forming a final dielectric thin film on the
upper surface of and around the sample; and then, the sample
returning to the vacuum transport chamber; and a sample take-out
step: the sample returning from the vacuum transport chamber to the
sample loading chamber through the vacuum transition chamber.
[0007] In the multilayer MTJ etching method of the present
invention, preferably, gas used in the etching or cleaning step in
the reactive ion plasma etching chamber is inert gas, nitrogen,
oxygen, fluorine-based gas, NH3, amino gas, CO, CO.sub.2, alcohol,
or a combination thereof; and the gas, power, airflows, and
pressure that are used in different steps are identical or
different.
[0008] In the multilayer MTJ etching method of the present
invention, preferably, gas used in the etching or cleaning step in
the IBE chamber is inert gas, nitrogen, oxygen, or a combination
thereof; and the gas, ion beam angles, ion beam energy, and ion
beam density that are used in different steps are identical or
different.
[0009] In the multilayer MTJ etching method of the present
invention, preferably, materials of the first dielectric thin film
and the final dielectric thin film are identical or different; the
material of the first dielectric thin film or the final dielectric
thin film is a group IV oxide, group IV nitride, group IV nitrogen
oxide, transition metal oxide, transition metal nitride, transition
metal nitrogen oxide, alkaline earth metal oxide, alkaline earth
metal nitride, alkaline earth metal nitrogen oxide, or a
combination thereof; and the materials of the first dielectric thin
film are identical or different in different first dielectric
coating steps.
[0010] An MRAM device is provided, which includes a multilayer MTJ
prepared by using the multilayer MTJ etching method according to
claim 1, where each isolation layer and a free layer above the
isolation layer in the multilayer MTJ present a step-like
structure.
[0011] A multilayer MTJ etching method is further provided, which
uses an etching device including a sample loading chamber, a vacuum
transition chamber, a reactive ion plasma etching chamber, an IBE
chamber, a film coating chamber, and a vacuum transport chamber,
where the vacuum transition chamber is connected to the sample
loading chamber and the vacuum transport chamber separately in a
linkable manner; the reactive ion plasma etching chamber, the IBE
chamber, and the film coating chamber are separately connected to
the vacuum transport chamber in a linkable manner; a sample is
processed without interrupting the vacuum, and the reactive ion
plasma etching chamber and the IBE chamber are separately used at
least one time. The method includes the following steps: a sample
loading step: loading the sample to the sample loading chamber, and
the sample entering the vacuum transport chamber through the vacuum
transition chamber, wherein the sample is formed on a semiconductor
substrate and includes a bottom electrode, an MTJ, a cap layer, and
a mask layer; the MTJ includes a pinned layer, an isolation layer,
and a free layer; and there are multiple isolation layers and free
layers; a first etching step: the sample entering the IBE chamber
or the reactive ion plasma etching chamber, etching the sample, and
stopping etching at a particular isolation layer; and then the
sample returning to the vacuum transport chamber; a first cleaning
step: the sample entering the reactive ion plasma etching chamber
or the IBE chamber, and removing metallic residues and treating a
sample surface, so that metal contamination and a sidewall damage
layer formed in the first etching step are completely removed; and
then the sample returning to the vacuum transport chamber; a first
dielectric coating step: the sample entering the film coating
chamber, and forming a first dielectric thin film on the upper
surface of and around the sample; and then the sample returning to
the vacuum transport chamber; a first dielectric thin film opening
step: the sample entering the reactive ion plasma etching chamber
or the IBE chamber, opening the first dielectric thin film on the
top and bottom portions of the device but leaving the part on a
device sidewall, and stopping etching; and then the sample
returning to the vacuum transport chamber; a second etching step:
the sample entering the reactive ion plasma etching chamber or the
IBE chamber, etching the remaining layers of the sample, and
stopping etching at a bottom electrode metal layer; and then the
sample returning to the vacuum transport chamber; a second cleaning
step: the sample entering the IBE chamber or the reactive ion
plasma etching chamber, and removing metallic residues and treating
a sample surface, so that the metal contamination and sidewall
damage layer formed in the second etching step are completely
removed; and then the sample returning to the vacuum transport
chamber; a second dielectric coating step: the sample entering the
film coating chamber for coating protection, and forming a second
dielectric thin film on the upper surface of and around the sample;
and then, the sample returning to the vacuum transport chamber; and
a sample take-out step: the sample returning from the vacuum
transport chamber to the sample loading chamber through the vacuum
transition chamber.
[0012] In the multilayer MTJ etching method of the present
invention, preferably, an etching or cleaning angle in the IBE
chamber ranges from 10.degree. to 80.degree., which is an included
angle between an ion beam and a normal face of a sample stage.
[0013] In the multilayer MTJ etching method of the present
invention, the first dielectric thin film has a thickness of 0.5 nm
to 5 nm, and the second dielectric thin film has a thickness of 1
nm to 500 nm.
[0014] In the multilayer MTJ etching method of the present
invention, the MTJ sidewall with a thickness of 0.1 nm to 10.0 nm
is removed separately in the first cleaning step and the second
cleaning step.
[0015] An MRAM device is provided, which includes a multilayer MTJ
prepared by using the multilayer MTJ etching method according to
claim 6, where an isolation layer at which etching is stopped in
the first etching step and a free layer above the isolation layer
in the multilayer MTJ present a step-like structure.
[0016] In the present invention, the processing of the multilayer
MTJ is always in a vacuum environment, thereby avoiding the impact
of an external environment on etching. By means of the process of
combining etching and cleaning, a device structure maintains good
steepness, and the metal contamination and damage to an MTJ film
structure are significantly decreased, thereby greatly improving
the performance and reliability of a device. In addition, use of
both the IBE chamber and the reactive ion plasma etching chamber
solves the technical problem of an existing single etching method,
and improves production efficiency and etching process
precision.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a functional block diagram of an etching device
used in an MTJ etching method of the present invention;
[0018] FIG. 2 is a schematic structural diagram of a sample
containing a multilayer MTJ;
[0019] FIG. 3 is a flowchart of an embodiment of an MTJ etching
method;
[0020] FIG. 4 is a schematic structural diagram of a device formed
after etching to a first isolation layer and cleaning;
[0021] FIG. 5 is a schematic structural diagram of a device formed
after a first dielectric coating step;
[0022] FIG. 6 is a schematic structural diagram of a device formed
after etching to a second isolation layer and cleaning;
[0023] FIG. 7 is a schematic structural diagram of a device formed
after repetition of the first dielectric coating step;
[0024] FIG. 8 is a schematic structural diagram of a device formed
after etching to a bottommost isolation layer and cleaning;
[0025] FIG. 9 is a schematic structural diagram of a device formed
after etching to a bottom electrode metal layer and cleaning;
[0026] FIG. 10 is a schematic structural diagram of a device formed
after a final dielectric coating step;
[0027] FIG. 11 is a flowchart of another embodiment of an MTJ
etching method;
[0028] FIG. 12 is a schematic structural diagram of a device formed
after a first cleaning step;
[0029] FIG. 13 is a schematic structural diagram of a device formed
after a first dielectric coating step;
[0030] FIG. 14 is a schematic structural diagram of a device formed
after a first dielectric thin film opening step;
[0031] FIG. 15 is a schematic structural diagram of a device formed
after a second cleaning step; and
[0032] FIG. 16 is a schematic structural diagram of a device formed
after a second dielectric coating step.
DESCRIPTION OF THE EMBODIMENTS
[0033] To make the objective, technical solutions, and advantages
of the present invention clearer, the technical solutions in the
embodiments of the present invention are clearly and completely
described below with reference to the accompanying drawings in the
embodiments of the present invention. It should be noted that, the
specific embodiments described herein are merely used for
explaining the present invention, rather than limiting the present
invention. The described embodiments are some rather than all of
the embodiments of the present invention.
[0034] Based on the described embodiments of the present invention,
other embodiments acquired by those of ordinary skill in the art
without creative effort all belong to the protection scope of the
present invention.
[0035] In the description of the present invention, it should be
noted that, the orientation or positional relationship indicated by
the terms "upper", "lower", "vertical", "horizontal", etc. are
based on the orientation or positional relationship shown in the
accompanying drawings, and are only used for the convenience of
describing the present invention and simplifying the description,
rather than indicating or implying that the denoted device or
element must have a specific orientation or be constructed and
operated in a specific orientation. Therefore, these terms cannot
be construed as limitations to the present invention. In addition,
the terms "first" and "second" are merely used for description, but
are not construed as indication or implying relative
importance.
[0036] In addition, many specific details of the present invention,
such as the structure, material, dimensions, and treatment process
and technique of the device, are described below for a clearer
understanding of the present invention. However, as those skilled
in the art can understand, the present invention may not be
implemented according to these specific details.
[0037] Unless otherwise indicated below, various parts of the
device may be made of materials known to those skilled in the art
or materials with similar functions developed in the future.
[0038] A device used in an MTJ etching method of the present
invention is described below with reference to the accompanying
drawings. FIG. 1 is a functional block diagram of an etching device
used in the MTJ etching method of the present invention. As shown
in FIG. 1, the etching device includes a reactive ion plasma
etching chamber 10, an IBE chamber 11, a film coating chamber 12, a
vacuum transport chamber 13, a vacuum transition chamber 14, and a
sample loading chamber 15. The vacuum transition chamber 14 is
connected to the sample loading chamber 15 and the vacuum transport
chamber 13 separately in a linkable manner. The reactive ion plasma
etching chamber 10, the IBE chamber 11, and the film coating
chamber 12 are separately connected to the vacuum transport chamber
13 in a linkable manner. In addition, there may be multiple
chambers of each type.
[0039] The reactive ion plasma etching chamber 10 may be an
inductively coupled plasma (ICP) chamber, a capacitively coupled
plasma (CCP) chamber, a helicon wave plasma chamber, or the like.
The IBE chamber 11 may be an ion beam etching chamber, a neutral
particle beam etching chamber, or the like. The film coating
chamber 12 may be a physical vapor deposition (PVD) coating
chamber; and may also be a chemical vapor deposition (CVD) coating
chamber, such as a pulsed CVD coating chamber, a plasma enhanced
chemical vapor deposition (PECVD) coating chamber, an ICP-PECVD
coating chamber, an atomic layer deposition (ALD) coating chamber,
or the like.
[0040] In addition, the etching device further includes a sample
transfer system for realizing sample delivery between the chambers,
a control system for controlling the chambers and the sample
transfer system, a vacuum pumping system for achieving a vacuum
degree required by each chamber, a cooling system, and other
functional units included in a conventional etching device. These
device structures may all be implemented by those skilled in the
art by using existing technology.
[0041] Before etching of a multilayer MTJ, a structure to be etched
and containing a multilayer MTJ is formed on a semiconductor
substrate. FIG. 2 is a schematic structural diagram of a device to
be etched and containing a multilayer MTJ. As shown in FIG. 2, the
structure to be etched includes a bottom electrode metal layer 100,
an MTJ, a cap layer 104, and a hard mask layer 105, where the MTJ
includes a pinned layer 101, an isolation layer 102, and a free
layer 103. There are multiple isolation layers 102 and free layers
103 which are alternately formed on the pinned layer 101. The
thickness and material of each layer and the number of the layers
are selected according to actual requirements. For ease of
description, the isolation layers 102 are described below as a
first isolation layer, a second isolation layer, and a third
isolation layer from top to bottom.
[0042] FIG. 3 is a flowchart of an embodiment of a multilayer MTJ
etching method. As shown in FIG. 3, in a sample loading step S11, a
sample is loaded to the sample loading chamber 15 and enters the
vacuum transport chamber 13 through the vacuum transition chamber
14.
[0043] Afterwards, in a first etching step S12, the sample enters
the reactive ion plasma etching chamber 10, and is etched by using
reactive ion plasma. Etching is stopped at the first isolation
layer. Then, the sample returns to the vacuum transport chamber 13.
Gas used in the reactive ion plasma etching chamber may be inert
gas, nitrogen, oxygen, fluorine-based gas, NH3, amino gas, CO, CO2,
alcohol, or the like. It is required to realize device separation
and achieve steepness required by the device during etching.
[0044] Minimal metal contamination such as contamination less than
1 nm may be produced and a Nano-scale damage layer may also be
formed on the MTJ sidewall during etching. Therefore, subsequently,
in a first cleaning step S13, the sample enters the IBE chamber 11,
and metallic residues are removed and the sample surface is treated
by using ion beams. Then the sample returns to the vacuum transport
chamber 13. Gas used in the IBE chamber may be inert gas, nitrogen,
oxygen, or the like. An IBE angle preferably ranges from 10.degree.
to 80.degree., which is an included angle between the ion beam and
a normal face of a wafer. Preferably, 0.1 nm to 10.0 nm MTJ
sidewall is removed, so that the metal contamination and the
sidewall damage layer formed in the first etching step are
completely removed. FIG. 4 is a schematic structural diagram of a
device formed after the first cleaning step.
[0045] Afterwards, in a first dielectric coating step S14, the
sample enters the film coating chamber 12 and a first dielectric
thin film 106 is formed on the upper surface of and around the
sample which has been subjected to the foregoing etching process;
and then the sample returns to the vacuum transport chamber 13.
FIG. 5 is a schematic structural diagram of a device formed after
the first dielectric coating step. The first dielectric thin film
106 formed by coating is a dielectric material capable of realizing
separation of adjacent MTJ devices, which may be, for example, a
group IV oxide, group IV nitride, group IV nitrogen oxide,
transition metal oxide, transition metal nitride, transition metal
nitrogen oxide, alkaline earth metal oxide, alkaline earth metal
nitride, alkaline earth metal nitrogen oxide, or the like. The
first dielectric thin film may have a thickness of above 0.5 nm but
below 50 nm. By the first dielectric coating step, the sidewall of
the opened MTJ can be prevented from damage by plasma in the
subsequent etching process.
[0046] Then in a first dielectric thin film opening step S15, the
sample which has been subjected to film coating in the foregoing
step enters the reactive ion plasma etching chamber 10, and the
first dielectric thin film 106 is etched by using reactive ion
plasma, so that the first dielectric thin film 106 on the top and
bottom portions of the device is etched away. Because the thickness
of the first dielectric thin film formed on the MTJ sidewall is
greater than that of the first dielectric thin film formed on the
horizontal surface, part of the first dielectric thin film 106
still remains on the MTJ sidewall.
[0047] The sample continuously stays in the reactive ion plasma
etching chamber 10, the first etching step S12 is repeated to etch
the sample by using reactive ion plasma, and etching is stopped at
the second isolation layer. Then, the first cleaning step S13 is
repeated to remove metal contamination and sidewall damage, to
obtain a structure shown in FIG. 6. The first dielectric coating
step S14 is repeated to form a first dielectric thin film on the
structure which has been subjected to the foregoing second etching
and cleaning, to obtain a structure shown in FIG. 7. Then, the
first dielectric thin film opening step S15 is continuously
performed. By leaving part of the dielectric thin film on the
sidewall of the etched MTJ, the sidewall of the opened MTJ can be
prevented from damage by plasma in the subsequent etching process.
Afterwards, steps S12 to S15 are repeated and etching is performed
until the bottommost isolation layer, as shown in FIG. 8.
[0048] Subsequently, a final etching step S16 is performed. The MTJ
is continuously etched in the reactive ion plasma etching chamber
10, and etching is stopped at the bottom electrode metal layer 100.
The used gas may be inert gas, nitrogen, oxygen, fluorine-based
gas, NH.sub.3, amino gas, CO, CO.sub.2, alcohol, or the like.
Because the opened MTJ is protected by the first dielectric thin
film 106, it is not required to consider the damage to the film
layers of the protected MTJ in subsequent etching and thus the used
etching gas can be selected from a wider range.
[0049] Then in a final cleaning step S17, the sample enters the IBE
chamber 11, and metallic residues are removed and the sample
surface is treated by using ion beams, so that the metal
contamination and the sidewall damage layer formed in the foregoing
etching step are completely removed. Then, the sample returns to
the vacuum transport chamber 13. Gas used in the IBE chamber may be
inert gas, nitrogen, oxygen, or the like. An IBE angle preferably
ranges from 10.degree. to 80.degree., and preferably, 0.1 nm to
10.0 nm MTJ sidewall is removed. After the foregoing etching and
cleaning steps, the device sidewall is clean and complete
separation is realized. FIG. 9 is a schematic structural diagram of
a device formed after the final cleaning step.
[0050] Afterwards, in a final dielectric coating step S18, the
sample enters the film coating chamber 12 for coating protection,
and a final dielectric thin film 107 is formed on the upper surface
of and around the sample. Then, the sample returns to the vacuum
transport chamber 13. The material of the final dielectric thin
film may be a group IV oxide, group IV nitride, group IV nitrogen
oxide, transition metal oxide, transition metal nitride, transition
metal nitrogen oxide, alkaline earth metal oxide, alkaline earth
metal nitride, alkaline earth metal nitrogen oxide, or other
dielectric materials capable of realizing separation of adjacent
MTJ devices. The final dielectric thin film may have a thickness of
above 1 nm but below 500 nm. The final dielectric coating step can
prevent the device from damage when exposed to the atmosphere in
the subsequent process, and further can realize complete insulation
and isolation between devices. FIG. 10 is a schematic structural
diagram of a device formed after the final dielectric coating
step.
[0051] Finally, in a sample take-out step S19, the sample returns
from the vacuum transport chamber 13 to the sample loading chamber
15 through the vacuum transition chamber 14.
[0052] The above merely describes one specific embodiment of the
multilayer MTJ etching method of the present invention, but the
present invention is not limited thereto. In other embodiments of
the multilayer MTJ etching method of the present invention, the
first etching step, the final etching step, and the first
dielectric thin film opening step may also be performed in the IBE
chamber by using ion beams to complete etching. The first and final
cleaning steps may also be performed in the reactive ion plasma
etching chamber by using reactive ion plasma to complete cleaning.
That is to say, each etching step and each cleaning step may be
performed in the reactive ion plasma etching chamber or the IBE
chamber by selection, thus realizing multiple possible
technological processes. These technological processes all fall
within the protection scope of the present invention. However,
considering from the production efficiency and the precision of the
etching process, the present invention does not adopt a solution in
which all the etching and cleaning steps are performed in the same
chamber (the IBE chamber or the reactive ion plasma etching
chamber). In other words, the reactive ion plasma etching chamber
and the IBE chamber must be separately used at least one time in
the MTJ etching method of the present invention. In addition,
specific implementations of the steps may vary from each other
according to different conditions. In the etching or cleaning steps
in the IBE chamber, the gas, ion beam angles, ion beam energy, and
ion beam density that are used in different steps may be identical
or different. In the etching or cleaning steps in the reactive ion
plasma etching chamber, the gas, power, airflows, and pressure that
are used in different steps may be identical or different.
[0053] In this embodiment, the processing of the MTJ is always in a
vacuum environment, thereby avoiding the impact of an external
environment on etching. Further, the isolation layers and the free
layers are all subjected to etching, cleaning, and coating
protection in different steps, thus significantly alleviating the
metal contamination and damage to the MTJ film structure and
greatly improving device performance and reliability. In addition,
use of both the IBE chamber and the reactive ion plasma etching
chamber solves the problems caused by a single etching method in
the prior art, and improves production efficiency and etching
process precision.
[0054] Moreover, in an MTJ formed according to the foregoing
embodiment of the multilayer MTJ etching method, as shown in FIG.
10, each isolation layer 102 and the free layer 103 above the
isolation layer present a step-like structure. Accordingly, an MRAM
device containing the multilayer MTJ also has such a feature.
[0055] FIG. 11 is a flowchart of another embodiment of a multilayer
MTJ etching method. Subsequently, in a sample loading step S21, a
sample is loaded to a sample loading chamber 15, and enters a
vacuum transport chamber 13 through a vacuum transition chamber
14.
[0056] In a first etching step S22, the sample enters an IBE
chamber 11 and is etched by using ion beams. Etching is stopped at
a second isolation layer, and then the sample returns to the vacuum
transport chamber 13. Gas used in the IBE chamber may be inert gas,
nitrogen, oxygen, or the like; and an IBE angle preferably ranges
from 10.degree. to 80.degree..
[0057] Then in a first cleaning step S23, the sample enters a
reactive ion plasma etching chamber 10, and is cleaned by using
reactive ion plasma, to remove metal contamination and sidewall
damage. An obtained structure is shown in FIG. 12. Afterwards, the
sample returns to the vacuum transport chamber 13. Preferably, an
MTJ sidewall with a thickness of 0.1 nm to 10.0 nm is removed, so
that the metal contamination and the sidewall damage are completely
removed. Gas used in the reactive ion plasma etching chamber may be
inert gas, nitrogen, oxygen, fluorine-based gas, NH.sub.3, amino
gas, CO, CO.sub.2, alcohol, or the like.
[0058] Afterwards, in a first dielectric coating step S24, the
sample enters a film coating chamber 12 and a first dielectric thin
film 106 is formed on the upper surface of and around the sample
which has been subjected to the foregoing etching process; and then
the sample returns to the vacuum transport chamber 13. FIG. 13 is a
schematic structural diagram of a device formed after the first
dielectric coating step. The first dielectric thin film 106 formed
by coating is a dielectric material capable of realizing separation
of adjacent MTJ devices, which may be, for example, a group IV
oxide, group IV nitride, group IV nitrogen oxide, transition metal
oxide, transition metal nitride, transition metal nitrogen oxide,
alkaline earth metal oxide, alkaline earth metal nitride, alkaline
earth metal nitrogen oxide, or the like. The first dielectric thin
film may have a thickness of above 0.5 nm but below 50 nm. By the
first dielectric coating step, the sidewall of the opened MTJ can
be prevented from damage by plasma in the subsequent etching
process.
[0059] Then in a first dielectric thin film opening step S25, the
sample which has been subjected to film coating in the foregoing
step enters the reactive ion plasma etching chamber 10, and the
first dielectric thin film is etched by using reactive ion plasma,
so that the first dielectric thin film on the top and bottom
portions of the device is etched away. Because the thickness of the
first dielectric thin film formed on the MTJ sidewall is greater
than that of the first dielectric thin film formed on the
horizontal surface, part of the first dielectric thin film 106
still remains on the MTJ sidewall. An etching endpoint of the first
dielectric thin film is defined by using an automatic optical
endpoint detector in the reactive ion etching chamber. FIG. 14 is a
schematic structural diagram of a device formed after the first
dielectric thin film opening step.
[0060] Subsequently, in a second etching step S26, the multilayer
MTJ is continuously etched in the reactive ion plasma etching
chamber 10, and etching is stopped at a bottom electrode metal
layer 100. The used gas may be inert gas, nitrogen, oxygen,
fluorine-based gas, NH3, amino gas, CO, CO2, alcohol, or the like.
The gas used in this step may be identical with or different from
that used in the first etching step. Because the opened MTJ is
protected by the first dielectric thin film 108, it is not required
to consider the damage to the film layers of the protected MTJ in
subsequent etching and thus the used etching gas can be selected
from a wider range.
[0061] Then in a second cleaning step S27, the sample enters the
IBE chamber 11, and metallic residues are removed and the sample
surface is treated by using ion beams, so that the metal
contamination and the sidewall damage layer formed in the foregoing
etching step are completely removed. Then, the sample returns to
the vacuum transport chamber 13. Gas used in the IBE chamber may be
inert gas, nitrogen, oxygen, or the like. An IBE angle preferably
ranges from 10.degree. to 80.degree., and preferably, 0.1 nm to
10.0 nm MTJ sidewall is removed. After the foregoing etching and
cleaning steps, the device sidewall is clean and complete
separation is realized. FIG.
[0062] 15 is a schematic structural diagram of a device formed
after the second cleaning step.
[0063] Afterwards, in a second dielectric coating step S28, the
sample enters the film coating chamber 12 for coating protection,
and a second dielectric thin film 107 is formed on the upper
surface of and around the sample. Then, the sample returns to the
vacuum transport chamber 13. The material of the second dielectric
thin film may be a group IV oxide, group IV nitride, group
[0064] IV nitrogen oxide, transition metal oxide, transition metal
nitride, transition metal nitrogen oxide, alkaline earth metal
oxide, alkaline earth metal nitride, alkaline earth metal nitrogen
oxide, or other dielectric materials capable of realizing
separation of adjacent MTJ devices. The second dielectric thin film
may have a thickness of above 1 nm but below 500 nm. The second
dielectric coating step can prevent the device from damage when
exposed to the atmosphere in the subsequent process, and further
can realize complete insulation and isolation between devices.
[0065] FIG. 16 is a schematic structural diagram of a device formed
after the second dielectric coating step.
[0066] Finally, in a sample take-out step S29, the sample returns
from the vacuum transport chamber 13 to the sample loading chamber
15 through the vacuum transition chamber 14.
[0067] The above merely describes one specific embodiment of the
multilayer MTJ etching method of the present invention, but the
present invention is not limited thereto. In other embodiments of
the multilayer MTJ etching method of the present invention, the
first etching step may also be stopped at any other isolation
layer, such as the first isolation layer, the third isolation
layer, the fourth isolation layer, or the like. In addition, the
first etching step may also be performed in the reactive ion plasma
etching chamber, and the second etching step may also be performed
in the IBE chamber. That is to say, each etching step and each
cleaning step may be performed in the reactive ion plasma etching
chamber or the IBE chamber by selection, thus realizing multiple
possible technological processes. These technological processes all
fall within the protection scope of the present invention. However,
considering from the production efficiency and the precision of the
etching process, the present invention does not adopt a solution in
which all the etching and cleaning steps are performed in the same
chamber (the IBE chamber or the reactive ion plasma etching
chamber). In other words, the reactive ion plasma etching chamber
and the IBE chamber must be separately used at least one time in
the multilayer MTJ etching method of the present invention. In
addition, specific implementations of the steps may vary from each
other according to different conditions. In the etching or cleaning
steps in the IBE chamber, the gas, ion beam angles, ion beam
energy, and ion beam density that are used in different steps may
be identical or different. In the etching or cleaning steps in the
reactive ion plasma etching chamber, the gas, power, airflows, and
pressure that are used in different steps may be identical or
different.
[0068] In this embodiment, the processing of the multilayer MTJ is
always in a vacuum environment, thereby avoiding the impact of an
external environment on etching. By means of the process of
combining etching and cleaning, a device structure maintains good
steepness, and the metal contamination and damage to an MTJ film
structure are significantly decreased, thereby greatly improving
the performance and reliability of a device. In addition, use of
both the IBE chamber and the reactive ion plasma etching chamber
solves the technical problem of an existing single etching method,
and improves production efficiency and etching process
precision.
[0069] Moreover, in an MTJ formed according to the foregoing
embodiment of the multilayer MTJ etching method, as shown in FIG.
16, the second isolation layer 102 and the free layer 103 above the
second isolation layer present a step-like structure. Accordingly,
an MRAM device containing the multilayer MTJ also has such a
feature. Definitely, the present invention is not limited thereto.
When the first etching step is stopped at another isolation layer,
for example, the third isolation layer or the fourth isolation
layer, this isolation layer and the free layer above it together
present a step-like structure.
[0070] The above merely describes a preferred embodiment of the
present invention, but the protection scope of the present
invention is not limited thereto. Changes or replacements easily
conceived by any person skilled in the art within the technical
scope of the present invention all fall within the protection scope
of the present invention.
* * * * *